In order to clarify the mechanism behind antiferromagnetic (AFM)-ferromagnetic (FM) phase transition, we investigate the electronic and magnetic structures of FeRh by using first principles calculations with the GGA + U method. By choosing the appropriate values of the on-site Coulomb interaction (U) of Fe_3d and Rh_4d electrons, we succeed in explaining the reported AFM-FM phase transition experiments for the first time by obtaining the total energy difference between the AFM and FM states (ΔE). Other physical quantities such as the density of states (DOS) are also consistent with experimental reports.

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  We improve our model calculation for heat-assisted magnetic recording (HAMR) by introducing the concept of the recording time window proposed in the micromagnetic calculation. The improved model calculation includes all the equations for the HAMR conditions used in the previous model. The difference is the introduction of the recording time window to determine the composition of the medium and the writing field. This improvement means that the results obtained using the model calculation become consistent with those obtained using a micromagnetic calculation. The minimum anisotropy constant ratio of the medium at 2, 3, and 4 Tbpsi can be determined using the improved model calculation.

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  The coercivity mechanism of Nd-Fe-B thin film samples with and without Nd deposition was investigated by simultaneous chemical and magnetic imaging by means of X-ray magnetic circular dichroism-photoemission electron microscopy. The two Nd-Fe-B thin film samples exhibited almost the same surface morphology and magnetic domain patterns, but their coercive fields were quite different, being 0.98 T for the sample with Nd deposition and 0.55 T for sample without Nd deposition. The chemical distribution of Nd revealed that Nd aggregates with the average size of 130 nm exist, and the density in the Nd-deposited sample is much higher than that in the not deposited one. A comparison of the magnetic and chemical contrast images implied that the Nd aggregates act as domain wall pinning sites, indicating that the large coercivity difference in the Nd-Fe-B thin films would be attributable to the different density of wall pinning sites.

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  In order to investigate the effect of lattice mismatch between FePt thin films and single crystal substrates on the tetragonality and the magnetization process, FePt thin films have been fabricated on MgAl₂O₄ (MAO) (100) and MgO (100) single crystalline substrates at a substrate temperature of 700 °C. The Fe concentration in the FePt films was varied from 45.0 to 50.8 at. %. In addition to the fundamental (002) peak, (001) and (003) superlattice peaks have clearly been observed in the X-ray diffraction patterns for all the samples, indicating the formation of L1₀ ordered structure. The magnetization measurements show that all the samples are perpendicularly magnetized. Large coercivity (Hc) of 57.8 kOe and 54.4 kOe was observed for the films with Fe_49.3Pt_50.7 and Fe_48.3Pt_51.7 (at. %) deposited on MgO and MAO substrates, respectively. It was confirmed that good hard magnetic properties can be obtained for the Fe₄₉Pt₅₁ (at. %) thin film.

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  Fe_100–xSi_x (x = 0, 2, 6, 10 at. %) alloy films are prepared on MgO single-crystal substrates of (001), (110), and (111) orientations at temperatures ranging between room temperature and 600 °C by using a radio-frequency magnetron sputtering system. The film growth behavior, the crystallographic properties, and the magnetic properties are systematically investigated. Fe-Si(001) single-crystal films with bcc structure are formed on MgO(001) substrates. The Fe-Si films deposited on MgO(110) substrates consist of epitaxial bcc(211) bi-crystals whose orientations are rotated around the film normal by 180° each other. Fe-Si films grow epitaxially on MgO(111) substrates with two types of bcc(110) variant whose crystallographic orientations are similar to the Nishiyama-Wasserman and the Kurdjumov-Sachs relationships. The orientation dispersion of Fe-Si film decreases with decreasing the Si composition, with increasing the substrate temperature, and with decreasing the index of the substrate crystallographic plane. The Fe-Si films deposited on MgO(001) and (110) show in-plane magnetic anisotropies reflecting the magnetocrystalline anisotropies of bulk Fe-Si alloy crystals. The Fe-Si films deposited on MgO(111) show nearly isotropic in-plane magnetic anisotropies that possibly come from the multiple variant structure. The coercivity decreases with increasing the Si composition and with decreasing the substrate temperature.

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  Bismuth substituted gadolinium iron garnet thin films (Bi_xGd_3-xFe₅O₁₂) were prepared with x = 1, 2, and 2.5 on glass substrates by enhanced metal organic decomposition (EMOD) method. We mixed the solution containing Fe₂O₃, Bi₂O₃ and Gd₂O₃ carboxylates so that we could obtain desired Bi content x. X-ray diffraction (XRD), optical transmittance / reflectivity, and Faraday rotation (FR) were measured for characterizations in order to examine their dependence on annealing temperatures and different amount of Bismuth substitution (x). When Bi_xGd_3-xFe₅O₁₂ thin films were directly prepared on glass substrates, Bi₂O₃ phase were observed by XRD measurements and with increasing Bi content x from 1 to 2, the FR increased from 1.2 to 5.8 deg./μm at the wavelength of 530 nm. FR of Bi_2.5Gd_0.5Fe₅O₁₂ thin films prepared directly on glass substrates were smaller (0.35 deg./μm) than those with x = 2. When Bi_2.5Gd_0.5Fe₅O₁₂ thin films were prepared with annealing temperature of 620°C with Gd₃Fe₅O₁₂ buffer layer on glass substrates, the films showed garnet crystal structure and FR, which is comparable with that of Bi_2.5Gd_0.5Fe₅O₁₂ thin films prepared on (111) (GdCa)₃(GaMgZr)₅O₁₂ (SGGG) single crystal substrates. These results demonstrate that Bi_xGd_3-xFe₅O₁₂ thin films can be prepared on glass substrates with controlled Bi content and that FR as high as that prepared on the SGGG substrate can be obtained by the EMOD method.

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  This study presents a method for determining the demagnetization characteristics of ferrite magnets based on reluctance network analysis (RNA). First, an RNA model for determining the operating points of a magnet considering demagnetization using a two-straight-line approximation of the demagnetization curve is discussed. Then, using the proposed model, demagnetization characteristics are determined. Experimental results demonstrate the validity of the proposed method.

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  In previous studies, we applied reluctance network analysis (RNA) to the dynamic analysis of the induction motor. However, the accuracy of our analysis of the motor characteristics using the RNA model was not high because the detailed magnetic flux distribution in the rotor was not taken into account. In this paper, we propose a 3D RNA model that considers the detailed magnetic flux distribution in the rotor and skew of the rotor bar. Using the proposed RNA model, the winding currents of the induction motor under no-load and locked rotor conditions can be calculated with higher accuracy than with the previous RNA model.

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  A suspension of core-shell particles composed of a biodegradable polymer core and iron oxide nanoparticles (IONPs) exhibits higher heat generation under an alternating magnetic field compared with a suspension of IONPs at the same IONP concentration. The improvement of the heat generation will be attributed to the change of the strength of dipolar interactions between adjacent IONPs. The IONPs in the core-shell particles were relatively isolated, in contrast with that in IONP suspension before the formation of the core-shell particles. Therefore, in the core-shell particles, the dipolar interaction is reduced, and the heat-generating capability is increased. This explanation is brought through investigating the influence of the agglomerate size of IONPs on the heat-generating capability.

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